Bloodhype

Five hundred thousand years ago, the ancient Tar-Aiym civilization trapped something they clearly considered too dangerous to leave loose: the Vom, an amoeba-like entity of enormous size and appetite. When an AAnn commander unearths and hauls it to the planet Repler for study, he has no idea what he's really brought home. Meanwhile, Church intelligence agents are chasing a resurgence of the incurably addictive drug bloodhype, a trail that leads to a freighter captain used as an unwitting mule and, eventually, to a young smuggler named Flinx working undercover inside the trade. Alan Dean Foster's Humanx Commonwealth novel, early chronologically in the Pip & Flinx series though written second.